Quinolone derivatives having a 3-(cyclopropyl-aminomethyl)pyrrolidinyl group are disclosed in JP-A-59-67269 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), but a quinolone derivative according to the present invention which has a substituent derived from the cycloalkylaminomethylpyrrolidine compound at the 7-position and a substituent other than a halogen atom at the 8-position and may also have a substituent at the 5-position is unknown.
Recently, many synthetic quinolone antimicrobial agents excellent in not only antimicrobial activity but also in oral absorbability, distribution property to organ, and excretion rate have been developed and provided for clinical use as a chemotherapeutic agent effective on various infectious diseases.
However, low sensitive bacteria resistant to these drugs have recently been increasing in the medicinal field. Further, bacteria resistant to drugs other than quinolone antimicrobial agents have also been acquiring resistance to quinolone antimicrobial agents, as .beta.-lactam resistant Staphylococcus aureaus (MRSA). Therefore more effective drugs have been keenly demanded in the field of medicine.
The antimicrobial activity, efficacy and safety of quinolone antimicrobial agents are largely influenced by the substituents at the 7- and 1-positions. And at the same time, the substituents at the 5- and 8-positions also have considerable role to those features. The inventors of the present invention have considered that proper assortment of proper substituents to these positions could provide compounds excellent in antimicrobial activity, efficacy and safety. They have extensively studied seeking a compound exhibiting high antimicrobial activity on a broad range of bacteria including quinolone-resistant bacteria. As a result, it has been found that a quinolone compound having a substituent derived from a cycloalkylaminomethylpyrrolidine compound at the 7-position and having a substituent other than a halogen atom at the 8-position exhibits potent antimicrobial activity toward Gram negative bacteria and Gram positive bacteria, especially Gram positive bacteria including MRSA. It has also been found that the compound additionally having a substituent at the 5-position shows similarly excellent antimicrobial activity.
It has further been found that the compound having a halogenocyclopropyl group, particularly a fluorocyclopropyl group, at the 1-position is excellent in efficacy and safety as well as antimicrobial activity. The present invention has been completed based on these findings.
Of the quinolone derivatives of the present invention having a substituted cyclic alkyl group, e.g., a halogenocyclopropyl group, at the 1-position, a pair of enantiomers attributed only to the halogenocyclopropane ring are present even when there is no stereoisomerism in the substituent at the other position. This is ascribed to the steric relationship between the pyridonecarboxylic acid moiety and the halogen atom on the cyclopropane ring. It is possible to apply a racemic mixture of the enantiomers as a drug as such.
Where stereoisomerism exists at other position in addition to the halogenocyclopropane moiety, particularly at the 7-positioned substituent, such a quinolone derivative embraces diastereomers, that is, at least 4 kinds of stereoisomers are possible. A mixture of diastereomers is a mixture of isomers having different physical properties and is hardly applicable as a drug as such.
The present inventors have made an effort to obtain a quinolone compound as a pure stereoisomer even if there are diastereomers, particularly a pure stereoisomer of 1-(1,2-cis-2-fluorocyclopropyl)-substituted quinolone derivative.
As a result, the present inventors have succeeded in separately obtaining each enantiomer of cis-2-fluorocyclopropylamine as a pure isomer. Starting with this cis-fluorocyclopropylamine, they separately obtained each enantiomer of a quinolone derivative attributed only to the steric configuration of the fluorocyclopropane ring thereof. They also succeeded in obtaining each enantiomer of a cycloalkylaminomethylpyrrolidine compound having an asymmetric carbon atom as a pure isomer.
Now that the above-mentioned quinolone derivative and cycloalkylaminomehylpyrrolidine compound useful as an intermediate have been obtained, it is possible to synthesize an optically active quinolone derivative substantially comprising a pure diastereomer.